1. Field of the Invention
The present invention relates to a hermetically sealed storage battery such as nickel-hydrogen storage battery, nickel-cadmium storage battery and lithium ion battery. More particularly, the present invention relates to a hermetically sealed storage battery provided with a cover body for hermetically sealing an opening formed therein such as opening for gas exhaust and opening for injection of electrolytic solution.
2. Description of the Related Art
In general, a hermetically sealed storage battery such as nickel-hydrogen storage battery, nickel-cadmium storage battery and lithium ion battery is prepared by a process which comprises inserting an electricity-generating element having a positive electrode and a negative electrode laminated on each other with a separator provided interposed between into a closed-end rectangular cylindrical metallic can, injecting an electrolytic solution into the can, and then welding a sealing plate to the opening of the can. The sealing plate is provided with a gas vent for exhausting a gas generated in the battery. A metallic cover body provided with an elastic valve (safety valve device) is disposed in the gas vent. The metallic cover body is welded to the sealing plate at the periphery thereof to seal the battery.
Referring now to the operation of the metallic cover body provided with an elastic valve body, since the elastic valve body is compressed, the interior of the battery can be kept air-tight while the cover body is mounted on the battery. When a gas is produced in the battery to raise the inner pressure beyond a predetermined value, the elastic valve body is compression deformed to allow the gas to be readily released. When the inner pressure of the battery falls below the predetermined value, the elastic valve body is released from the compression and then spontaneously restored to keep the interior of the battery air-tight again.
However, since the foregoing elastic valve body is merely kept inserted in the metallic cover body until the metallic cover body is mounted on the gas vent in the sealing plate, vibration developed during the preparation of the battery, e.g., during the transportation of the cover body causes the elastic valve body to come off from the metallic cover body, lowering the production yield.
Therefore, a means has been employed involving the bonding of the elastic valve body to the cover body with an adhesive for the purpose of preventing the elastic valve body from coming off from the metallic cover body due to vibration during the production of battery, i.e., transportation of the cover body. However, it is difficult to uniformalize the coated amount of adhesive, making it impossible to obtain expected effects. Further, the facilities required to make the coated amount of adhesive constant are not simple, complicating the production.
The present invention has thus been worked out in the light of the foregoing problems. An object of the present invention is to provide a battery structure such that an elastic valve body or the like cannot easily come off from the cover body during the production of the battery and hence enhance the production yield.
In order to solve the foregoing problems, a first aspect of the present invention is a hermetically sealed storage battery comprising a cover body for hermetically sealing an opening provided in a storage battery, wherein the cover body comprises: a flange portion airtightly fixed to the opening; a bulge portion protruding from the flange portion and provided with a space in which an elastic body is mounted, and a hook portion formed on an inner wall of the bulge portion, for keeping an annular rim formed on the peripheral side wall protruding outwardly of the elastic valve body, wherein the elastic valve body is held by the hook portion and the annular rim so that it can be prevented from coming off from the cover body.
A second aspect of the battery is a hermetically sealed storage battery according to the first aspect, wherein the hook portion comprises a protrusion portion protruding inwardly of a lowest end of the side wall of the bulge portion formed on an inner wall of the bulge portion, and the annular rim is hooked by the protrusion portion.
A third aspect of the battery is a hermetically sealed storage battery according to the second aspect, wherein the protrusion portion comprises a plurality of protrusions for hooking the annular rim at the end of the protrusions.
A fourth aspect of the battery is a hermetically sealed storage battery according to the third aspect, wherein the protrusion portion comprises a pair of protrusions protruding slant-inwardly from two positions being symmetrical to each other.
A fifth aspect of the battery is a hermetically sealed storage battery according to the second aspect, wherein the bulge portion is provided with an opening for ventilation on the side wall thereof and the elastic body constitutes an elastic valve body.
By arranging the cover body as mentioned above, the elastic valve body can be kept by the protrusion portion and the annular rim prevented from coming off from the cover body, making it possible to prevent the elastic valve body from coming off from the metallic cover body due to vibration, e.g., during the transportation of the cover body and hence enhance the production yield. Further, since no adhesive for holding the elastic valve body is required, production facilities and control are simple, making it easy for this type of cover body to be mounted.
A sixth aspect of the battery is a hermetically sealed storage battery according to the second aspect, wherein the outer diameter of the annular rim is greater than the distance between the protrusion portions.
By providing the elastic valve body with an annular rim on the peripheral side wall thereof protruding outwardly of the elastic valve body in such an arrangement that the outer diameter of the annular rim is greater than the distance between the protrusion portions and the annular rim comes in contact with the inner wall of the cover body, the mispositioning of the elastic valve body can be prevented, making it assured that the elastic valve body can be compression-deformed when the inner pressure of the battery reaches the predetermined value and thus can sufficiently serve as a safety valve as well as maintain airtightness. At this time, the protrusion portion is kept separated from the elastic valve body. In other words, the distance between the protrusion portions is smaller than the outer diameter of the annular rim of the elastic valve body and greater than the outer diameter of the peripheral side wall of the elastic valve body.
A seventh aspect of the battery is a hermetically sealed storage battery according to the second aspect, wherein the hook portion is an inclined portion on the inner side wall of the bulge portion running inwardly of the ceiling thereof toward the flange portion.
An eighth aspect of the battery is a hermetically sealed storage battery according to the seventh aspect, wherein the bulge portion is provided with an opening for ventilation on the side wall thereof and the elastic body constitutes an elastic valve body.
A ninth aspect of the battery is a hermetically sealed storage battery according to the seventh aspect, wherein the outer diameter of the annular rim is greater than the minimum distance between the inclined portions.
A tenth aspect of the battery is a hermetically sealed storage battery according to the seventh aspect, wherein the elastic body is mounted so as to contact with the inner side wall and the ceiling of the bulge portion.
Even if the bulge portion is provided with an inclined surface on the inner wall thereof extending inwardly of the ceiling of the bulge portion toward the flange portion instead of providing a protrusion portion at a part of the side wall of the bulge portion protruding inwardly of the side wall, the elastic valve body can be held in almost the same manner as mentioned above.
Moreover, in accordance with the invention, an elastic body having no safety valve function can be held in the cover body instead of elastic valve body, making it possible to prevent the elastic body from coming off from the cover body due to vibration developed during the transportation of the cover body as well as seal airtightly an opening provided in the battery such as injection port.